This can also be performed while "walking your fingers" like “Itsy Bitsy Spider”. I found these instructions at PolishForums.com:

Put your right hand to the left and the left to the right so that palms are facing out.

Then you start putting your fingers on top of each other starting with your pinky and moving up. This represents the chimney sweeper walking up the ladder. Then you twist your hands without losing the hold of your fingers so that the hands form a basket with your thumb sticking out. That's the chimney sweeper in chimney.